This invention relates to the palladium-catalyzed amination of conjugated dienes to produce long-chain unsaturated amines.
Recently, several publications have reported on the palladium-catalyzed linear dimerization of conjugated dienes, such as butadiene, with addition of amines; Takahashi, Bull. Chem. Soc. Japan 41, 454-60 (1968). According to one of these methods, the palladium catalyst is modified with a phenoxide anion catalyst promoter as described in U.S. Pat. Nos. 3,350,451 and 3,444,202. Another reported method employs a palladium complex with phosphine ligands such as triethylphosphine, tributylphosphine and triphenylphospine; U.S. Pat. No. 3,530,187 and British patent specification No. 1,178,812. In all of these methods, long-chain amines are synthesized by use of primary or secondary amines in the amination reaction.
In still another publication, the direct amination of butadiene with ammonia is described by Mitsuyasu et al; Chem. Comm. (Japan), 345 (1971). The reaction is reported to take place in acetonitrile solvent and in the presence of palladium acetate and triphenylphosphine. However, the reaction is narrow in scope and sensitive to conditions. Moreover, the rates of amination using the catalyst system described by Mitsuyasu are low and yields are poor.
Development of a practical method for the rapid addition of ammonia or amines to butadiene to produce long-chain unsaturated amines in high yields would provide significant advantages in simplicity of reaction and cost reduction.